Beam tomography systems and methods

Abstract

In some embodiments, a velocity model for a seismic exploration subsurface volume is updated by beam tomography. A set of beams is generated from an input seismic data set, and a beam group is assembled for each beam. Each beam group includes the original beam and a set of related beams (if any). If no related beams are found for a given original beam, the original beam is discarded. The beams in a group are then aligned vertically (in depth or time), and a tomography matrix is assembled from the alignment adjustment values for the beams. The tomography matrix is used to perform a tomographic update of the velocity model, and the updated velocity model is used to generate an image of the subsurface volume. The described systems/methods allow efficiently generating accurate images of subsurface volumes, including in areas having complex geologic structures, allowing reduced image inaccuracies/artifacts.

What is claimed is: 
     
       1. A seismic data processing method comprising employing a computer system including at least one processor to:
 generate a plurality of seismic data beams according to seismic trace data characterizing a subsurface volume; 
 for a selected beam of the plurality of beams, identify a beam group comprising the selected beam and a set of beams meeting a relatedness condition relative to the selected beam; 
 determine a set of relative inter-beam time or depth shifts that align the beam group in time or depth; 
 build a tomography matrix according to a plurality of relative inter-beam time or depth shifts determined for a plurality of corresponding beam groups; 
 perform a tomographic update of a velocity model characterizing the subsurface volume according to the tomography matrix to generate an updated velocity model for generating a seismic image of the subsurface volume; and 
 generate the seismic image of the subsurface volume according to the updated velocity model, thereby reducing imaging artifacts in the seismic image. 
 
     
     
       2. The method of  claim 1 , wherein the relatedness condition includes a beam proximity condition. 
     
     
       3. The method of  claim 2 , wherein the relatedness condition further includes a beam dip deviation condition. 
     
     
       4. The method of  claim 3 , wherein the relatedness condition further includes an inter-beam cross-correlation condition. 
     
     
       5. The method of  claim 1 , wherein the method further comprises employing a graphical user interface to receive user input setting at least one value for a set of relatedness condition parameters. 
     
     
       6. The method of  claim 1 , wherein a set of relatedness condition parameters includes a maximum inter-beam distance. 
     
     
       7. The method of  claim 6 , wherein the set of relatedness condition parameters further includes a maximum inter-beam dip deviation. 
     
     
       8. The method of  claim 7 , wherein the set of relatedness condition parameters further includes an inter-beam cross-correlation value. 
     
     
       9. The method of  claim 1 , wherein the set of inter-beam time or depth shifts are time or depth shifts relative the selected beam. 
     
     
       10. The method of  claim 1 , wherein the tomography matrix comprises a plurality of rows each representing a corresponding beam group, and a plurality of columns each representing a corresponding voxel in the subsurface volume, wherein each entry in the tomography matrix includes a traveltime delay encountered or a distance traveled by the corresponding beams within the corresponding voxel. 
     
     
       11. A non-transitory computer-readable medium encoding instructions which, when executed by a computer system cause the computer system to:
 generate a plurality of seismic data beams according to seismic trace data characterizing a subsurface volume; 
 for a selected beam of the plurality of beams, identify a beam group comprising the selected beam and a set of beams meeting a relatedness condition relative to the selected beam; 
 determine a set of relative inter-beam time or depth shifts that align the beam group in time or depth; 
 build a tomography matrix according to a plurality of relative inter-beam time or depth shifts determined for a plurality of corresponding beam groups; 
 perform a tomographic update of a velocity model characterizing the subsurface volume according to the tomography matrix to generate an updated velocity model for generating a seismic image of the subsurface volume; and 
 generate the seismic image of the subsurface volume according to the updated velocity model, thereby reducing imaging artifacts in the seismic image. 
 
     
     
       12. The computer-readable medium of  claim 11 , wherein the relatedness condition includes a beam proximity condition. 
     
     
       13. The computer-readable medium of  claim 12 , wherein the relatedness condition further includes a beam dip deviation condition. 
     
     
       14. The computer-readable medium of  claim 13 , wherein the relatedness condition further includes an inter-beam cross-correlation condition. 
     
     
       15. The computer-readable medium of  claim 11 , wherein the method further comprises employing a graphical user interface to receive user input setting at least one value for a set of relatedness condition parameters. 
     
     
       16. The computer-readable medium of  claim 11 , wherein a set of relatedness condition parameters includes a maximum inter-beam distance. 
     
     
       17. The computer-readable medium of  claim 16 , wherein the set of relatedness condition parameters further includes a maximum inter-beam dip deviation. 
     
     
       18. The computer-readable medium of  claim 17 , wherein the set of relatedness condition parameters further includes an inter-beam cross-correlation value. 
     
     
       19. The computer-readable medium of  claim 11 , wherein the set of inter-beam time or depth shifts are time or depth shifts relative the selected beam. 
     
     
       20. The computer-readable medium of  claim 11 , wherein the tomography matrix comprises a plurality of rows each representing a corresponding beam group, and a plurality of columns each representing a corresponding voxel in the subsurface volume, wherein each entry in the tomography matrix includes a traveltime delay encountered or a distance traveled by the corresponding beams within the corresponding voxel. 
     
     
       21. A computer system comprising at least one processor programmed to:
 generate a plurality of seismic data beams according to seismic trace data characterizing a subsurface volume; 
 for a selected beam of the plurality of beams, identify a beam group comprising the selected beam and a set of beams meeting a relatedness condition relative to the selected beam; 
 determine a set of relative inter-beam time or depth shifts that align the beam group in time or depth; 
 build a tomography matrix according to a plurality of relative inter-beam time or depth shifts determined for a plurality of corresponding beam groups; 
 perform a tomographic update of a velocity model characterizing the subsurface volume according to the tomography matrix to generate an updated velocity model for generating a seismic image of the subsurface volume; and 
 generate the seismic image of the subsurface volume according to the updated velocity model, thereby reducing imaging artifacts in the seismic image.